Self-adjusting fan vane

ABSTRACT

A self-adjusting fan vane of synthetic resin has a narrow, thickened, inflexible portion at the leading edge attached to the periphery of the fan hub and an elastically flexible vane flap attached to the inflexible vane portion and freely movable in respect thereto. A latticed insert is embedded in the vane, the insert having a first set of webs extending rectilinearly along a concave surface of the vane in a direction tangential to the periphery of the hub and a second set of webs extending in a direction radial to the hub, the webs of the second set being corrugated.

[4 1 Aug. 26, 1975 1 1 SELF-ADJUSTING FAN VANE [75] Inventor: KarlheinzWitzel, Heidelberg,

Germany [73] Assignee: Walker Manufacturing Company,

Mannheim, Germany [22] Filed: Aug. 27, 1973 [21] App]. No.: 392,085

[52] US. Cl. 416/132; 416/224; 416/240; 416/241 [51] Int. Cl. F04c 29/38[58] Field of Search 416/132, 132 A, 240, 241 A, 416/139, 224

3,594,098 7/1971 Pratinidhi 416/240 X 3,637,325 1/1972 Morley 416/2303,751,181 8/1973 Hayashi 416/132 3,758,231 9/1973 Barnstead 416/132FORElGN PATENTS OR APPLICATIONS 2,013,481 10/1970 Germany 416/132Primary ExaminerEverette A. Powell, Jr. Attorney, Agent, or FirmKurtKelman 5 7 ABSTRACT A self-adjusting fan vane of synthetic resin has anarrow, thickened, inflexible portion at the leading edge attached tothe periphery of the fan hub and an elastically flexible vane flapattached to the inflexible vane portion and freely movable in respectthereto. A 1atticed insert is embedded in the vane, the insert having afirst set of webs extending rectilinearly along a concave surface of thevane in a direction tangential to the periphery of the hub and a secondset of webs ex tending in a direction radial to the hub, the webs of thesecond set being corrugated.

10 Claims, 10 Drawing Figures PATENTEU AUBZ 6 I975 SHEET 1 OF PA {ENTEDAUG 2 61875 sum 3 o PATENTEDAUBZBIQYS 3,901,625 SHEET 8 [IfSELF-ADJUSTING FAN VANE The present invention relates to improvements infans for internal combustion engines. j

Fans of this type are known wherein a plurality of vanes are attached tothe periphery of a hub mounted for rotation about its axis. A narrow.thickened. inflexible vane portion at the leading edge of the vane isattached to the periphery of the hub and an elastically flexible vaneflap is attached to the inflexible vane portion and is freely movable inrespect thereto.

In the design of such fans. care must be taken that there is sufficientcooling of the engine at low rotary speed of the fan and at low enginespeed. Such fans produce excessive and unneeded cooling at high andengine speeds. This unwanted cooling effect causes a considerableincrease in the power requirements of the fan which must be met by theengine.

It has been attempted to avoid this disadvantage by designing the fanvane so that such power-determining properties of the vane as the angleofincidence and the radius of curvature of the vane change at higherrotary speeds under the influence of the air flow and centrifu galforces. While this influences the efficiency in de pendence on therotary speed. it does not influence it in dependence on the ambienttemperature.

It has also been proposed to provide a laminated fan vane with layers ofdifferent coefficients of thermal expansion to cause changes in theangle ofincidence and the curvature of the vane in dependence on theambicnt temperature. This type of fan vane has the consid crablcdisadvantage that the thermal expansion extends in all directions.causing unfavorable effects of the efficicncy and increased fan noise.Also. the two layers. one of metal and the other of synthetic resin. arebonded together by an adhesive providing insufficient cohesion betweenthe layers and eventually causing the vane layers to separate under theinfluence of the constant form changes. A further disadvantage of thistype of vane is its high manufacturing cost because of the laborinvolved.

It is the primary object of this invention to overcome the abovedisadvantages of conventional fan vanes and to provide a vane which isselfadjusting by changing its form in dependence on the ambienttemperature as well as the air flow and centrifugal forces to which thevanes are subjected during rotation of the fan.

The above and other objects are accomplished in accordance with theinvention by embedding a Iatticcd insert in a vane ofsynthctic resin.The insert has a first set of webs extending rcctilinearly along aconcave sur face of the vane in a direction generally tangential to theperiphery of the hub. and a second set of webs ex tending in a directiongenerally radial to the hub. thc webs of the second set beingcorrugated. The corrugations of the webs of the second set extend in thedircction of the other surface of the vane opposite to the concavesurface thereof.

The insert may be of metal. for instance perforated sheet metal. a wiregrid or an expanded metal sheet. It may also consist of glass fibrereinforced synthetic resin.

According to one preferred feature. a narrow beaded portion forms thetrailing edge of the \anc. and weights are embedded in thc beadedportion.

The abovc and other objects. advantages and features ofthe presentinvention will become more apparent from the following detaileddescription of a now preferred embodiment thereof. taken in conjunctionwith the accompanying drawing wherein FIG. I is a partial front view ofafan according to this invention;

FIG. 2 is a fragmentary side view of the fan of FIG. 1'.

FIG. 3 is a section along line III-III of FIG. 1;

FIG. 4 is a section along lines line IV|V of FIG. 1;

FIGS. 5 and 6 are enlarged illustrations of the details shown at V andVI, respectively. of FIGS. 3 and 4;

FIG. 7 is similar to FIG. 6, showing a modification of the corrugatedinsert web;

FIG. 8 illustrates an embodiment of an insert. in top view;

FIG. 9 is a section along lines IXIX of FIG. 8; and

FIG. I0 is an end view of the insert of FIG. 8.

Referring now to the drawing and first to FIGS. 1 to 4, the illustratedfan comprises hub I mounted for rotation about its axis 10. A pluralityof self-adjusting vanes 2 of synthetic resin are distributed about theperiphery of the hub. either regularly or. if found desirable.irregularly spaced from each other. In operation. the fan rotatesclockwise in the direction of arrow 4 so as to present a leading edge 5and a trailing edge 9 to the incident air. A concave vane surface 17 andanother surface 20 axially offset from the surface 17, extend betweenthe leading and trailing edges of each vane.

The leading edge of the vane extends about perpendicularly to rotaryaxis I0 of the fan and about parallel to a radius of the hub. The outervane edge 7 extends about perpendicularly to the radius and is slightlycurved. as shown. to connect with trailing edge 9 by way of a roundedcorner 8. The trailing edge is about parallel to the leading edge 5. Ina conventional manner. the vanes are so mounted on the hub that theangle of incidence of the air decreases outwardly in a radial direction.

A narrow. thickendcd. inflexible vane portion 11 attachcs each vane tothe periphery of the hub at the leading edge of the vane. The vaneportion II is tapered in a radial direction. being narrower at the outerend than at the root. Thus. the wedge-shaped vane portion 11 has theflap 14 of the vane attached thereto along a line I2 which is inclinedin respect of the radius. which assures good use of the centrifugalforces. Flap 14 is elastically flexible and freely movable in respect ofinflexible portion 11. Under the influence of air flow and centrifugalforces at increased rotary speeds of the fan. the flap 14 is flexed.thus changing the angle of incidence and the radius of curvature of thefan vane. The effect of the centrifugal forces is increased by providinga narrow beaded portion 15 at the trailing edge 9 of the vane. and byloading the beaded portion with weight means. such as balls or a weight21.

The vanes 2 may consist of any suitable synthetic resin. such aspolypropylene. As best shown in FIGS. 3 and 4, a latticeshapcd insert 3is embedded in each vane. The coefficient of thermal expansion of theinsert material is lower than that of the synthetic resin forming thevane. A useful insert material is metal but a synthctic resin reinforcedwith glass fibres may also be used.

The insert has a first set of webs I6 extending along concave surface 17of the vane in parallel planes generally tangential to the periphery ofhuh I. As shown in FIG. I, the webs 16 extend across substantially theentire width of the vane 2. A second set of webs 18 con nect the webs l6and extend in a direction generally radial to the hub. Sections of webs18 between adjacent webs 16 are corrugated, the corrugations 19 thereofextending from webs 16 towards vane surface and having axes of curvatureextending in the common direction of elongation of webs 16.

In the embodiment shown in FIGS. 4 and 6, the corrugations I9 are aboutsemi-cylindrical about axes of curvature parallel to the direction ofelongation of webs I6 while the corrugations 19' in the modification ofFIG. 7 are flattened and form a pinched neck portion. The lattermodification provides a more secure connection of the insert with thevane since the corru gations I9 will more or less hook the webs 18 intothe synthetic resin material of the vane when the insert is embeddedtherein.

A useful embodiment of an insert is illustrated in the various views ofFIGS. 8 to 10. The specifically described and claimed web structure ofthe insert produces increased curving of vane 2 about the longitudinalaxes of webs 16 with an increase in the ambient temperature since thethermal expansion coefficient of the synthetic resin material of thevane considerably exceeds that of webs 16. On the other hand, thesynthetic resin material of the vane can expand independently of thelower thermal expansion coefficient of webs 19 in the direction thereof.Therefore, the vane will not be curved in this direction and will assumeform 2' (FIG. 2). At lower temperatures and under the influence of thecentrifugal forces, the vane will be flexed outwardly, as shown at 2" inFIG. 2.

Manufacture of the described vane is very simple. The insert 3 may beplaced in an injection mold, with the webs I6 flush against the moldwall, and the syn thetic resin is then injection molded about the insertto form the vane.

Since the insert webs 16 are flush with the surface of the vane, goodheat conductivity is assured so that the vanes will adapt very quicklyto temperature changes. Thus, the vanes of the present invention willoperate at optimal efficiency since such power-determining factors asthe angle of incidence and the curvature of the vane will change as adirect function of temperature changes as well as air flow andcentrifugal forces. Furthermore, the manufacture of the vanes is verysimple and a very good connection is provided between the insert and thevane.

What is claimed is:

I. In a fan for an internal combustion engine, in combination:

a. a hub having an axis of rotation and a periphery, and

b. a plurality of vanes extending radially from said periphery in spacedrelationship, each vane including a leading edge portion attached tosaid hub and substantially inflexible, and a flap attached to saidleading edge portion and more flexible than said edge portion, said flapincluding a trailing edge portion remote from said leading edge portionand having two axially offset surfaces connecting said edge portions,one of said surfaces being concavely arcuate about an axis of curvatureapproximately radial relative to said axis of rotation,

(i) said flap essentially consisting of synthetic resin composition anda lattice-shaped insert embedded in said composition, the insert beingof a material having a coefficient of thermal expansion smaller than thecoefficient of thermal expansion of said composition,

(2) said insert including two sets of webs, the webs of each set beingelongated in a common direction, being transversely spaced from eachother, and transversely intersecting the webs of the other set,

(3) the webs of one set being corrugated about axes of curvatureextending in the direction of elongation of the webs of the other set,the webs of said other set being elongated in a direction from one ofsaid edges toward the other edge.

2. In the fan of claim 1, the webs of the insert being of metal.

3. In the fan of claim 2, the insert consisting of perforated sheetmetal.

4. In the fan of claim 2, the insert consisting of a wire grid.

5. In the fan of claim 2, the insert consisting of an expanded sheetmetal.

6. In the fan of claim I, the insert consisting of glass fibrereinforced synthetic resin.

7. In the fan of claim I said trailing edge portion being beaded, andweight means embedded in the beaded portion.

8. In the fan of claim I, the webs of said one set having each aplurality of sections interposed between respective pairs of adjacentwebs of the other set, said sections being corrugated.

9. In the fan of claim 8, said webs of said other set beingsubstantially flush with said one surface, said c0rrugations projectingfrom the webs of said other set toward the other one of said twosurfaces of said flap.

10. In the fan of claim I, said sets being fixedly fastened to eachother.

1. In a fan for an internal combustion engine, in combination: a. a hubhaving an axis of rotation and a periphery, and b. a plurality of vanesextending radially from said periphery in spaced relationship, each vaneincluding a leading edge portion attached to said hub and substantiallyinflexible, and a flap attached to said leading edge portion and moreflexible than said edge portion, said flap including a trailing edgeportion remote from said leading edge portion and having two axiallyoffset surfaces connecting said edge portions, one of said surfacesbeing concavely arcuate about an axis of curvature approximately radialrelative to said axis of rotation, (1) said flap essentially consistingof synthetic resin composition and a lattice-shaped insert embedded insaid composition, the insert being of a material having a coefficient ofthermal expansion smaller than the coefficient of thermal expansion ofsaid composition, (2) said insert including two sets of webs, the websof each set being elongated in a common direction, being transverselyspaced from each other, and transversely intersecting the webs of theother set, (3) the webs of one set being corrugated about axes ofcurvature extending in the direction of elongation of the webs of theother set, the webs of said other set being elongated in a direcTionfrom one of said edges toward the other edge.
 2. In the fan of claim 1,the webs of the insert being of metal.
 3. In the fan of claim 2, theinsert consisting of perforated sheet metal.
 4. In the fan of claim 2,the insert consisting of a wire grid.
 5. In the fan of claim 2, theinsert consisting of an expanded sheet metal.
 6. In the fan of claim 1,the insert consisting of glass fibre reinforced synthetic resin.
 7. Inthe fan of claim 1 said trailing edge portion being beaded, and weightmeans embedded in the beaded portion.
 8. In the fan of claim 1, the websof said one set having each a plurality of sections interposed betweenrespective pairs of adjacent webs of the other set, said sections beingcorrugated.
 9. In the fan of claim 8, said webs of said other set beingsubstantially flush with said one surface, said corrugations projectingfrom the webs of said other set toward the other one of said twosurfaces of said flap.
 10. In the fan of claim 1, said sets beingfixedly fastened to each other.